Method of making ethyl chloride



Patented Nov. 16, 1948 METHOD OF MAKING ETHYL cnLonmE lloward W. Hill,Concord, and Eldred. L. Dance,

Berkeley, Calif., assignors to The Dow Chemical Company, Midland, Mich.,a corporation of Delaware No l)rawi ng. Application May l'i 1944,

, Serial No. 536,032

4Claims. (01.204-163) This invention relates to'methodsof makin ethylchloride, and has particular regard to improvements in making ethylchloride as the principal product of the chlorination of ethane.

In the chlorination of ethane by the action of gaseous chlorine the arthas employed various procedures. One well known procedure consists inexposing a mixture of ethane and chlorine to a source of actinic lightwhich induces and promotes the reaction. Such photochemical method isordinarily carried out at moderately elevated temperatures, on the orderof about .1009, to 300 0., cooling being employed to absorb a sufficientproportion of the heat of reaction that an excessive temperature rise inthe gaseous reaction mixture is prevented. The successive stages ofsubstitution of chlorine in a hydrocarbon molecule are known to overlapextensively, so that it is not practically possible by directchlorination of ethane to produce a single partial chlorination productto the exclusion of others.

The usual expedient in chlorinating ethane to obtainfethyl chloride asthe principal product is to employ a large excess of ethane, e. g., 6 to10 or more volumes of ethane per volume of chlorine, so as to minimizethe formation of dichlorethanes.

We have found that certain unexpected advantages are attained in thedirect photochemical chlorination of ethane to produce ethyl chloride,when mixtures of ethane with methane are em.- ployed instead of pureethane. Our investigations have shown that, for a particular C12/C2Hs 5ratio, a higher yield of ethyl chloride is obtained in chlorinating amixture of ethane and methane within the range hereinafter shown thanwhen pure ethane is chlorinated. This result is of great practicalvalue. V ethane are natural gas'and petroleum refinery gases, in whichethane is normally a minor component accompanied by a much largerproportion of methane. The separation of pure ethane from such gases :bythe usual methods of solvent extraction under pressure, followed byliquefaction of the hydrocarbon extract and fractionation of the same,is a costly procedure. 0n the other The commercial sources of i Y 2'rinated than is methane, so that in the chlorinationof a mixture ofmethane and ethane the latter is preferentially chlorinated to a greateror less" extent. For example, in U. S. Patent No; 1,908,312 is describeda method of purifying methane from small -amounts of ethane whichaccompany it by a partial chlorination in which the ethane ispreferentially chlorinated and the chlorinated ethanes are separatedfrom the methane;.;, :l-Iowever, the patented process depends upon acatalytic thermal chlorination at temperatures between 200 and 400 C. Inthe latter processconsiderably more than an equimolecular proportion ofchlorine to ethane is required for complete removal of the ethane, andunder the conditions employed the chlorinated ethanes formed consistlargely of the dichlor derivatives. The patented procedure is notadapted for the production of ethyl chloride in commercial yield.

According to our invention a mixture of ethane its volume of methane istaken, to which chlorine is added in the proportion of from about 0.6 to1.2

volumes of chlorine relative to the volume of ethane in the mixture. Themixed gases are then exposed to actinic light, as from a mercury vaporlamp, to cause reaction between the chlorine and ethane, the zone ofreaction being. cooled to prevent a temperature rise much above 200 C.Under the stated conditions ethane is chlorinated largely to ethylchloride together with a minor proportion of dichlorethanes, without,any substantial chlorination of methane. The chlorinated ethanederivatives are separated from the reaction product by the usualprocedure of condensation, followed by scrubbing with water or anaqueous alkali to remove acid impurities and finally :by fractionaldistillation of the liquid condensate. The yield of ethyl chloride, aswell as the ratio of ethyl chloride to dichlorethanes, is

hand the separation of a mixtureof ethane and methane in proportionswithin therange of our invention is simpler and more readilyaccomplished, so that such mixtures are obtainable at a lower cost forthe ethane content of.the same than is pure ethane. Aocordingto ourmethod the chlorination of such mixtures'of ethane and methane producesa high yield of ethyl'chloride substantially freefrom chlorinatedmethanes, the separation of which from'the residual .gas is easilyeffected. i

It is known that ethane is more readily chloconsiderably increased overthat obtainable by the chlorination of ethane alone, using the sameratio of chlorine to ethane.

. While. the relative proportions of ethane and methane in themixedgases to be used in practicing-the invention may vary from 3/1 to 1/3,theoptimum ratio is about 1/1, and the optimum ratio of chlorine toethane is likewise about 1/1. The favorable effector methane in themixture is not observed if the volumetric Clz/C'zl-Ic ratio ismaterially lower than 0.6, while if the ratio is higher than 1.2 somechlorination-of methane occurs. Cooling of thegaseous reactingmixture isimportant inorderto prevent an excessive temperature rise duetoliberation of the heat of reac-y about 100 and 200 C. If thetemperature is permitted to rise materially above 200 0. some crackingof the chlorinated ethanes is liable to occur, accompaniedby splitting,off of hydrogen chloride, which reduces the yield of ethyl chloride, andchlorination of ethylene thereby formed increases the proportion ofdichlorethanes in the product.

In order to illustrate the advantages of thein: vention a series oftests was carired out,- showing the results of varying the proportionsof methane to ethane, and of 5310mm to .Qethaneg I n th es e runs thehydrocarbon gas and chlorine were mixed in the dark, and the mixed gaseswere passed through a tubular glass reactor coil submerg ed in a waterbath. A 100-Watt mercury lamp was dis posed centrally within the coil toilluminate the gas stream traversing the coil. The rate of gas flow wascorrelated witli 'the length and diameter of thecoil to give an aveargeresidence time pifthe gases in the coil of from 1 to 1.5 seconds. Theheat or reaction heated the water bath to b'oiling The reaction gaseswere cooled to condense thelique; f able products, the liquid condensatewas scrubhed with water and aqueous all a1 i, and fractionally distilledto separate the components. p v I The results of the various runs areshown in the table.

4 1.2, at a temperature between 100 and 200 C., and separating ethylchloride from the reaction product.

v 2. The method of malgingethyl chloride which comprises addingchloriri'efto a xture of ethane and methane in which the ratio ofCH4/C2Hs is from 3/1 to 1/3; the chlorine being in amount such t t themolar r atio of 012 0211; is from 0.6 to 1.2, causing reaction betweenethane and chlorine by exposing the gaseous mixture to a source ofactinic light, while removing; heat from the reacting gases to maintainthe temperature thereof between 100 and 200 0.. andseparating ethylchloride from the a onprqd qih jlhe inethd of making ethyl chloridewhich comprises adding chlorine to an approximately equimol'ecularmixture of ethane and methane in such proportion that the ratio ofC12/C2I-Ie is between 0.0 and 1.2, gausin'g' reaction between ethane andqh e es. e eqei h a mi tu a source of a'etinic lightat a temperaturebetween 100? and 2:00? (1., arid separating ethyl chloride from thereaction prec nct. v I

fL Ifhe rnethod of making ethyl chloride which comprises forming agaseous mixture of ethane, methane and chlorine in" approximatelyequimolecular proportions. passing ,1 the mixture Table Gas Comp.Product, M01 Per Cent fiatib Per-,Cent PGLGGDC P 0.. CB/G Ha .2 .Yield a6 0111.01 0.15.01. 011501 Camel/01H" dill iien o t ane wi e hanr ee ie fproportions, isnot sigmficantwhen the igatio of Clz/CzI-Ie is 0:5 byvolu'ne, and no increase in yield of ethyl chloride H I of 0.09 (run 5) theyieldof hylchloride from a 'ix of eth n 54m inane 51 5 4 5 equaltogth'at resulting fro'ni chloririati'onof pure eth ne t a l H 644:1.030141 6) T e greatest gain in yield of ethylch'loride is slhowriWh'eraih 1 /02 5 r m is .93 (5111111 if-. f the wa d u ?l. i" w e. 1119ionly re umed in a substantial incr 'e'of tiipei heritage of ethaneconverted tochlorihated c'onipounds, but also of the percentage bf hylehlo'ride yie co e ration is showniruns 10, ll) 1 3; fb 111' 1555imethyl f I "f d a e S; as ,5 1 as in the' hig h er propo onlbfdichlorethanes 15 product; and lowe'nd yield of ethyl chloride. Thedich16rethanes' formed along with ethyl 51 101-155 consisted of mixture5r 1,1-dichloi' ethane, and 1,2 -dichlorethan, 1 whieh the' ratio 61 theformer to the latter was roughly 2/1'.

K275515115; H y H m 1. The method of making ethyl chloride whichcomprises reacting ethane in exposure to light and in the 514454 115 rfrom 1 3 to 3 times its volume of methane with gaseous chlorine in suchpropor-. tion that the ratio of C12/C2'H6 is between 0.6 and 1 55observed firuns .i-) that the efiect 5; 45 through a 26115 irradiatedbyactinie light to cause matter: i A irlii is m Number Country Date586,582 France Jan. '7, 1925 780 Great Britain 1915 oIHEitR'EFEREfio sEllis.t.al., Chemical Action of 1 Ultra-Violet Light, 1941; pages526-27...

.C'ross, Handbook of Petroleum, Asphalt and Natural Gas", 1928, Revised;page 548.

Hass et al'r, Industrial and Engineering Chemn r volumes; ?.5 -i33.3 9-.1

Eglofi. et.al.; Chemical Reviews, volume 8, 1931; pages25-26. a

The 155561 references are of 655665 in the

